Alloy steel and process of making the same



Patented Sept. .2, 1924.

UNITED STATES GEAR/LES TYN'DALE EVANS, 0F TITUSVILLE, PENNSYLVANIA.

ALLOY STEEL AND PROCESS OF MAKING THE SAME.

No Drawing. Application filed April 3,

To all whom it may concern,

Be it known that I, CHARLES TYNDALE EVANS, a citizen of the United States, residing at Titusville, county of Crawford, and State of Pennsylvania, have invented cer" tain new and useful Improvements in Alloy Steels and Processes of Making the Same, fully described and represented in the following specification.

This invention relates to improvements in alloy steels, particularly steels adapted for cutlery, and also relates to improvements in processes for making such steels.

The main object of the invention is to provide a steel which. when worked into the desired article as, for example, by forging at the' proper temperature andproperly hardened, will be substantially non-corrosive under the conditions to which such steel articles are subjected, while at-the same time having all th e valuable properties of the best cutlery steels.

A further object of the invention is to provide a process which may be readily carried out for the manufacture of the alloy steels constituting a part of this invention.

The product included in this invention comprises an alloy steel of the composition described hereinafter and pointed out in the claims, and the process comprises the steps which will first befully described and then set forth in the claims.

The alloy steel which represents the best embodiment of the invention consists of the following:

' Per cent.

Iron 83.9 Carbon 0.6 Chromium 7.0 Tungsten 7.0 Silicon 1.0 Manganese 0.5 Phosphorus 0.0 Sulphur 0.0

The above represents what might be called an ideal alloy for the purposes of the invention. In practice, it is not always possible to produce material having the analysis stated above. For example, it is rarely possible to have the alloy entirely free from phos horus or sulphur. It is very important, owever, to keep these ingredients as low as-possible.

In carrying out the invention in practice 1922. Serial No. 549,210.

invention Per cent.

Carbon 0.500 to 0.850 Chromium 6.770 to 7.530 Tungsten 6.36 to 8.080 Silicon 0.810 to 1.130 Manganese 0.500 to 0.700 Phosphorus about .012 Sulphur about l .018

The principal remaining ingredient is 1101'1.

Alloy steels of substantially the composition stated above have been worked into cutlery and have given results much superior to those obtained with chromium alloy steels heretofore known.

These new steels are readily worked, but when being hardened they should be heated to somewhat higher temperatures than are used when working common cutlery steels. Highly satisfactory results are obtained if the present steels are-hardened at a-temperature of about 2000 F. While they, can be hardened satisfacorily if heated to a temperature as low as about 1900 F. the desired results are obtained with greater ease and certainty if the heating be carried to about 2100 F.

The duration of the heat treatment is also of some importance, because the advantageous properties of the material are best developed by what may be termed a thorough soaking heat. While the length of time varies according to size of the material which is being worked, and therefore cannot well be stated in minutes, it suffices for those skilled in-the art of steel treatment to say that the steel alloy of the present invention should remain in the heating furnace at about 2000 F. for a somewhat longer time than is ordinarily considered necessary for a good high carbon cutlery steel.

It has been found that an alloy steel of the type set forth above, worked in the usual manner, and hardened scribed, gave cutlery articles of greatly improved properties. Not only was a fine cutby the methods de-v I the usual lery edge obtained, but this edge was capable of withstanding hard usage, that is to say; was maintained as well as with the very best high carbon cutlery steels. Furthermore, the materia had a high resistance to a permanent set, and was relatively tough ascompared with the prior steels high in chromium.

A further important advantage of these alloy steels is that after the heat treatment referred to above, they are non-corrosive under the normal conditions to which articles of cutlery are subjected. For example, a polished surface of the finished article will not rust or stain by the action of the air, organic acids, weak inorganic acids, alkalies, salt water or the like.

Owing to the hard close texture which may be given to this steel by treatment as described, it may be polished to a mirror surface and will retain such a polish indefinitely, possible a great advance in the mirror art.-

It is to be understood, however, that this property of non-oorrodibility is only developed by the'heat treatment hereinbefore described. Prior to this treatment the alloy steel is corrodi'ble. Furthermore, the noncorrosiveproperty' of the alloy steel when developed by the heat treatment and workmg is not confined merely to the surface of Y the material but seems to extend throughout the mass, This is important in cutlery articles because subsequent grinding does not lead to a corrodible surface.

In carrying out the process for the manufacture of the new product hereinbefore referred to, the starting materials or mix may be as follows:

7 Parts.

Iron' 707.50 Ferro-chromium 104.40 Tungsten powder 63.75

- nganeseuue 6.25 Silico-zirconium- Q e 13.75

' Ferro-silicon 4.35

Total Thismix ismeIted in the usual way, for example, as 1n the manufacture of crucible steel, It may then be cast into ingot form and worked down by-the usual methods of resultant product, viz., the

working crucible steel. The bars or rods are cut to lengths suitable for the articles which it is desired to produce, and these blanks are heated and forged into the de sired shatpes. Finally the material is hardene'd in the manner hereinbefore described and may be finished by tempering and polishing in the usual way. The particular point to which attention is called in connection with the aboveprocess is that-the start-' ing material comprises a zirconium compound, in this case silico-zirconium, yet the alloy steel, when so that the material seems to make.

starting material was as follows:

analyzed by the usual methods of analysis employed in the steel works, does not seem to show the presence of any zirconium. It may be possible that by some very refined methods of analysis some zirconium or zirconium compounds might be detected in the alloy steel. It may be, however,- that the zirconium compound merely performs the function of a scavenging material 'or deoxidizer in making the; original ingot, and hence does not appear in thealloy steel product. While the presence of zirconium in the mix seems to be'important in that with it the desired alloy steel may be produced with certainty, apparently the presence of zirconium in the alloy steel, if any is present there, is not controlling. This seems to be shown by the fact that substantially the same alloy steel having substantially the same desirable properties as hereinbefore pointed out has been produced by a modification of the above process in which the Parts. Iron 790 Ferro-chromium 105 Tungsten powder 75 Manganese 4 Ferro-silicon 26 Using this starting mixture, melting it,

casting it into an ingot, working it down toviously the alloy steel so produced could not have any zirconium .in it. By both processes the alloy steel product will give an analysis showing the same ingredients set forth on page 2 of this specification and in proportions falling within the limits there stated. It is to be noted, however, that the process carried out with the mixture containing silico-zirconium seems to be more reliable than the modified process given above' where the vsili'co-zirconium is omitted from the mixture.

Variations may be made in the compost tion of the alloy steel and in the process without departing from theinvention. v li or example, the carbon content may be 1ncreased to some extent, for example, up to about 1 per cent, therebygiving a harder steel, but in such case more care Wlll' be required in working the steel into finished articles. Where the carbon content is kept at about the higher limit of .85 shown in the table, page 2, itwill .be found that the temperature for hardening may be ke t regularly at about 1900 F. whereas wi 'a lower carboncontent this hardening temferro-chromium such as is used in making high-speed steels, the carbon content will run toward the higher limit given in the table. If it is desired to keep the carbon near the low limit,the mix should be made with a ferro-chromium lower in carbon or with the so-called carbon-free ferrochromium.

B somewhat reducing the silicon content whi e increasing the carbon content to a reasonable extent, the quality of the product and the ease of working it will not be affected injuriously, and at the same time the hardening temperatures may be kept down to around 1900 F. With low carbon content, the silicon may go as high as about 2.0 per cent.

Funthermore, an alloy steel which will develop fully the desired non-corrosive properties, when hardened at the lower temperature of around 1900, may be obtained by the addition of nickel. While the amount of nickel used may vary, I have found that 3-]; per cent is about as high as is necessary. When more than this amount is used there is always a danger of segregation of the nickel in the finished articles, and this may give a bad appearance to the polished article, and, possibly, may lead to some corrodibility.

As illustrating the use of nickel in the alloy steels of this invention, I submit the following examples in which first is stated the mixture tobe melted and then the analysis showing the essential ingredients of the respective alloy steels, viz.:

Mix.

Parts. Iron 725 Ferrochromium 105 Tungsten, powder 7 5 Ferro-silicon 20 Nickel .25 Nickel-zirconium 50. Manganese 5 Analysis.

Per cent. Carbon 0.618 Chromium 7.83 Tungsten 6.56 Manganese 0.61 Silicon 1.15 Nickel 3.28

The principal remaining ingredient is iron.

Parts. Iron 7 25 Ferro-chrornium 105 Tungsten, powder 7 5 Ferro-silicon 20 Nickel 25 Nickel-zirconium 50 Manganese '.L'.... 5

Analysis.

7 Per cent. Carbon 0.486 Chromium 7.58 Tungsten 6.26 Manganese 0.73 Silicon 1.09 Nickel 1 3.46

The principal remaining ingredient is 1ron.

These nickel-containing alloys gave very satisfactory results.

It is to be noted that in the first example of the product set forth on page 1 of this specification, the tungsten content is specified around 7 per cent I have found that more tungsten may be employed if desired. However, it is ordinarily not necessary to go. above 10 per cent tungsten, because tungsten is" an expensive material, yet sometimes it may be desirable to increase the percentage of it in order to get somewhat'harder steels. If, however, the tungsten is to be increased above 10% it becomes important to cut down the silicon content of the alloy I steel.

While in connection with the process I have described the use of zirconium in the mixture serving as a starting material,

I may use in place thereof cerium, or titan-' ium. In using these equivalents of the zirconium, they may be employed commercially in the form of the ferro-alloys.

The manganese content of the alloy may sometimes be as low as 25%, particularly when the toughness of the resultant product is not important or where the iron used in making the mix is very pure. On the other hand, if copper is present as an impurity in the starting materials, which sometimes happens with certain irons, it may be well to run the man nese content of the alloy steel as high as The manganese seems to have the property of neutralizing any bad effects of the copper. My experience indicates thatthe manganese content has an effeet in determining the toughness of the finished product. However, I find no advanta e in using more than the high limit herein efore stated.

The chromium content may be reduced somewhat below the minimum limit stated in the formula on page 2 without materially departing from the qualities of the finished product. For example,'the chromium. content may be as low as 6%.

A steel containing less than 7% of tungsten will be satisfactory for some purposes where the cutting edge is not subjected to a very severe usage as, for example, with fruit knives or the llke. In this case the tungsten content may be reduced as low as 4% in the allow steel, but, as before indicated, with a slight loss in the durability of the cutting edge...

"mium content of not What is claimed is:

1. A ferrous alloy having a carbon content of not more than about 1%, a chroless than 6% and not more than about 7.53%, tent of more than about 4%. y

2. A ferrous alloy having a carbon content of not more than about 1%, a chromium content of not less than 6% and not more than about 7.53%, a tungsten content of more than about 4%, and a'manganese content of .25-,;t0 .75%.

3. A ferrous alloy having a carbon content of not more than about 1%, a chromium.

content of not less than 6% and not more than about 7.53%, a silicon content of essential amount but not more than 2%, and a hardening ingredient such as tungsten not exceeding 10%.

4. A ferrous allo substantially free from phosphorus and su phur and having a carbon content of between .5 and .85 a chromium content of about 6 to 7.53%, a tungsten content of more than 6%, a silicon content of essential amount but less than 2%, and a manganese content of about .5 to .7

5. A ferrous alloy. having a carbon content of not more than about 1%, a' chromium content of not less than 6% and not more than about 7.53%, a hardening ingredient such as tungsten not exceeding 10%, and which, when hardened at a suificiently high temperature, develops the property of noncorrosiveness, substantially as described.

and a tungsten con 6. The process of making a non-corrosive, wrought ferrous article',.. which consists in mixing the in edients to give the desired percentages 0 iron, chromium, tungsten, manganese and silicon in the finished article, together with zirconium, cerium or titanium, then melting the mixture, working it into the desired article and hardening at a temperature high enough to develop the non-corrosive properties, substantially as'described.

7. A ferrous allo substantially free from phosphorus and su phur and having a carbon content of between .5 and .85%, a chromium content of about 6 to 7.53%, a tungsten content of more than 6%, a silicon content of less than 2%, a manganese content of about .5 to .7%, and nickel in substantial amount but not more than 3 8. The process of making a non-corrosive, wrought ferrous article, which consists in mixing the in edients to desired percentages o iron, nicke chromium, tungsten, manganese and silicon in the finished article, together with zirconium, cerium or titanium, then melting the mixture, working it into the desired article and hardening at a temperature high enough to develo the non-corrosive properties substantia 1y as described.

Intestimony whereof, I have hereunto set my hand.v

CHARLES TYNDALE EVANS.

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